The invention relates to an apparatus for fuel injection and ignition for use in an internal combustion engine which burns and converts fuel, such as gasoline, diesel fuel, natural gas, alcohol, hydrogen, etc., into power, and a method of operation thereof.
In internal combustion engines, in order to improve fuel consumption efficiency, it is necessary to form a lean fuel-air mixture which is low in fuel concentration, to increase thermal efficiency by providing a high compression ratio and to burn instantaneously the lean fuel-air mixture.
In FIGS. 2a to 2f, various kinds of conventional combustion methods of spark ignition in engines, such as gasoline engines, are illustrated in schematic diagrams of combustion conditions viewed from the upper side of the engine cylinder.
FIG. 2a shows a general case of engines, wherein a flame kernel is formed in a fuel-air mixture by a spark plug 3, and the flame is propagated in the circumferential direction to burn the fuel-air mixture. This combustion method has a defect in that the flame blows out midway in the combustion when the mixture of gas and air is lean. Further, the flame propagation is slow, and the thermal efficiency is low.
As measures against these defects, it is proposed to arrange a plurality of spark plugs in the cylinder, as shown in FIG. 2b; however, the arrangement of the spark plugs can not be optimized because of the presence of an intake valve and an exhaust valve (not shown).
Further, a method of forming ignition sources by mixing exhaust gas of high temperature into a fuel-air mixture is proposed, as shown in FIG. 2c. However, the positions of the ignition sources change with each engine cycle, so that the thermal efficiency is low.
On the other hand, there also is a method of promoting flame propagation by increasing the energy of a spark plug 3 to produce high temperature plasma and jetting it into a combustion chamber, as shown in FIG. 2d. However, the penetration force of the plasma is small, and the thermal efficiency is low.
Further, as for the plasma as shown in FIG. 2d, a method of forming an activated jet, as described in SAE Technical paper 910565 has been proposed; however, the force of the jet is small, and the jet is blown away by the flow of the fuel-air mixture, so that a sufficient effect has not been achieved with this method as yet.
Further, as shown in FIG. 2e, there is proposed a method of promoting flame propagation by providing an auxiliary chamber 22, burning a fuel-air mixture in the auxiliary chamber 22 using a spark plug 3, and jetting a torch flame into the combustion chamber 21. However, the surface area of the combustion chamber 21 is larger than the auxiliary chamber 22, so that thermal efficiency thereof is lowered.
On the other hand, as shown in FIG. 2f, a method of directly igniting fuel, sprayed by a fuel injection valve 2, using a spark plug 3 is proposed. However, mixing of the sprayed fuel and air is insufficient, so that there is a disadvantage that some soot is produced.
As mentioned above, the conventional combustion methods have defects in that the thermal efficiency is low and some soot is produced, irrespective of the kinds of fuel, such as gasoline, natural gas, hydrogen, alcohol, etc., being used
Next, various kinds of conventional combustion methods used in auto-ignition engines, such as diesel engines, are illustrated in FIGS. 3a to 3f, each of which is a schematic diagram of combustion conditions viewed from an upper side of the engine cylinder.
FIG. 3a relates in general to diesel engines, wherein a spray of fuel from a fuel injection valve 2 is ignited by auto-ignition and flames are formed after a operation delay of ignition. For this time, some soot is produced when the mixing of the sprayed fuel and air is insufficient.
In order to eliminate this disadvantage, as shown in FIG. 3b, a method of promoting combustion by providing an auxiliary chamber 22 has been proposed. However, the surface area of the combustion chamber 21 is larger than that of the auxiliary chamber 22, and so the thermal efficiency is low.
Further, as shown in FIG. 3c, an attempt has been made to raise the pressure in a fuel injection valve 2 to 300 arm or more, to promote mixing of the air with gas and to prevent formation of soot. However, the timing of the auto-ignition is not fixed in each engine cycle and is not spatially consistent, so that the thermal efficiency is low.
Further, as shown in FIG. 3d, a method of promoting ignition of sprayed main fuel by injecting pilot fuel first to form a flame kernel has been proposed. However, the timing of formation of the flame kernel is not fixed in each engine cycle and spatially consistent, so that the thermal efficiency is low.
Further, as shown in FIG. 3e, a method of promoting combustion by providing a heater 23, such as a glow plug, has been proposed. However, the timing of the auto-ignition is not fixed in each engine cycle and is not spatially consistent, so that the thermal efficiency thereof is also low.
Furthermore, as shown in FIG. 3f, a method of igniting a fuel-air mixture by a flame produced in an auxiliary chamber or a nozzle has been proposed. However, the timing of the auto-ignition in the auxiliary chamber or the nozzle is not fixed in each engine cycle and is not spatially consistent, so that the thermal efficiency is low.
As mentioned above, in the conventional combustion methods as shown in FIGS. 2 and 3, except for the method as shown in FIG. 2b in which a plurality of spark plugs are employed, combustion is not fixed, but is changeable in each engine cycle and is not spatially consistent, so that the thermal efficiency is low.
Further, in the method shown in FIG. 2b, since it is difficult practically to position the plurality of plugs because of the presence of an intake valve and an exhaust valve, it is impossible to arrange the plugs in optimum positions, and as a result, the conventional method has the disadvantage that the thermal efficiency is low.